Conventionally, as for the use of yeast cell wall fraction, attempts have been made to develop film material from yeast. Japanese Patent Publication No. 56-19971, for example, discloses an edible protein film based on water-soluble proteins produced by removing the yeast cell membrane components from residual yeast which was produced by extracting nucleic acid. Japanese Laid-Open Patent Application No. 53-45385 discloses a method for producing a film, wherein the cells of a microorganism such as yeast are heated and alkali treated, acid is added for treatment involving isoelectric precipitation, the pH of the resulting precipitate is adjusted to between 6 and 8, and a plasticizer is added to the resulting gel-forming microorganism cells to produce a constituent.
Further, Publication of Patent No. 3349677 (Japanese Laid-Open Patent Application No. 2000-44878) describes: a coating agent whose primary component comprises yeast cell wall fractions comprising cell residue obtained by removing the internal soluble cell components of enzyme-treated yeast; and also the use of the coating agent or the coating agent comprising a plasticizer as a coating agent or as a coating film. Examples of its excellent properties include that this coating agent is able to coat even in a disperse medium of 100% water, affords a nonsticky finish despite its viscosity, thus resulting in coated particles and/or granules that do not aggregate, and further having a function to control release time. Moreover, it is shown that a film formed from the coating agent has a property that it has an extremely low oxygen permeability coefficient under dried conditions.
However, the coating agent described in Publication of U.S. Pat. No. 3,349,677 has an extremely excellent film property, when the film coating agent described in the patent publication is used, as it has a color of yellow-brown to brown, the coating agent or the making tablet agent has a bad-looking compared to the substances to be wrapped, changes of properties can be misidentified (for example, mistaken as mold, or mistaken the color to degradation etc.), and therefore result to delay of detecting deterioration.
Moreover, regarding the coating agent described in the patent publication, as the yeast cell wall fraction itself comprises relatively many proteins (21% as weight ratio), or lipid (8.0% as weight ratio), colorization due to oxidation of lipid and the like during preservation could happen.
Furthermore, the yeast cell wall fraction itself has some odor derived from yeast (hereinafter mentioned as yeast odor), therefore when the coating is made for flavor components, while maintaining the intended flavor component on one side, there was a risk that the flavor necessary was masked or impaired by the yeast odor of the yeast cell wall fraction itself. Thus, it was necessary to limit the additive level low and there was a problem that sufficient ability could not be exerted.
Further, as a mechanical property of the film itself, it is inferior for flexibility (plasticity), and relatively brittle. In some combinations of substances to be wrapped, films happened to be breakable due to environmental changes such as outer humidity.
On the other hand, when using the yeast cell wall fraction, it is already known to decolorize/deodorize the yeast cell wall fraction. In the Japanese Laid-Open Patent Application No. 4-248968, a method for treating yeast extract residue with alkali and acid, then decolorize with ozone and to treat with ethanol before and after the ozone treatment is described. Japanese Laid-Open Patent Publication No. 6-504191 discloses a method for treating yeast residue being acidified after treatment with alkali, hydrogen peroxide and the like, and its treated substances; U.S. Pat. No. 3,407,125 (Japanese Laid-Open Patent Application No. 9-103266) discloses a method for treating yeast autolytic insoluble substance with alkali, after suspending the substances with ethanol.
However, with these conventional methods, when the treatment for decolorization/deodorization is performed, the treated substances could be degenerated and loose their properties, or the film property or the film disintegrating property could be lost if the original form and structure are changed. Moreover, if it is decolorized while maintaining the film property or film disintegrating property, it could happen that it could not be decolorized to the intended level, and so on. Therefore, there were various limits for its use.
As for decolorization and deodorization of yeast extract residue and the like, attempts have been made conventionally. However, when the conventionally-performed methods of decolorization, described in for example, Japanese Laid-Open Patent Application No. 4-248968 (method of decolorizing and deodorizing yeast extract residue), Japanese Laid-Open Patent Application No. 6-70751 (yeast fragment product) or in Published Japanese Translation of PCT International Publication No. 6-504191 (treatment of yeast residue and products obtained thereof), that is methods for conducting heating treatment under high-alkaline condition (including reflux boiling etc.) or heating treatment under highly-acid condition (including reflux boiling etc.), removing soluble components and the like, and treating with agents such as hydrogen peroxide or reacting with ozone and the like, or reacting bleaching agents such as hypochlorous acid, are directly applied to the decolorization treatment of yeast cell wall fraction, there was a problem that the excellent property of the yeast cell wall fraction as described above is abolished in the obtained decolorized yeast cell wall fractions.
On the other hand, as for pharmaceutical, it is rare that drug component is directly administered in the form of chemical compound, and dosage forms are prepared by compounding pharmaceutical additives to dissolute drug component according to its purpose. There are various pharmaceutical additives, and one of them is exemplified.
For example, EUDRAGIT LS30-D55 used as an aqueous coating agent for medical use had problems to be a non-natural substance, with low gas-barrier property, and that film disintegration property is worse when the coating level was increased. Therefore, an aqueous coating agent from natural product, having high gas-barrier property, effect for preventing volatilization of perfume component, odor and the like, and sufficient disintegration property was awaited. Furthermore, the yeast cell wall fraction of the Patent Publication No. 3349677 is aqueous, derived from natural substance, having high gas-barrier property, film property, and good film-disintegration property, but as it has a color and odor of yeast, one without color and odor was awaited. Moreover, for HPC or HPMC used for binder, when the added level is increased, disintegration of granulation could be delayed. The yeast cell wall fractions show strong binding when dried, while showing rapid disintegration in water, therefore it is a disintegrated agent having binding ability. However, as it shows a color of yellow-brown to brown, the resulting granulation would have a color yellow-brown to brown. Therefore a colorless one was awaited.
Moreover, as a capsule substrate, gelatin, water-soluble polymer (hydroxymethyl ethyl cellulose), pullulan, polyvinyl alcohol (PVA) and the like are known, but they have problems such as difficulties in control release, deterioration of agents due to low oxygen-barrier property, safety of material (BSE or synthetic compounds) and the like.
As for resolving these problems, attempts to use yeast cell wall fractions as capsule substrate were made, and were described in Japanese Laid-Open Patent Application Nos. 2002-38133 and 2003-70428. However, in these methods, as yeast cell wall fraction has a color of yellow-brown to brown, there were problems that the resulting capsules would be yellow-brown to brown, or that the yeast cell wall fraction itself was colored as many proteins or lipids were contained in the yeast cell wall fraction.
The object of the present invention is to provide a decolorized yeast cell wall fraction being decolorized and deodorized, wherein the color and odor from yeast cell wall fraction have been removed, having excellent film property, preferably having physical properties that film disintegration property and excellent gas barrier property of the formed film have been maintained and improved, a method for producing the same, use of the decolorized yeast cell wall fraction as a coating agent, and further a coated material treated with the coating agent, and the like.
Yeast cell wall fractions such as yeast cell wall fraction (YCW) comprising cell residue obtained by removing the internal soluble cell components of enzyme-treated yeast, or acid-treated yeast cell wall fractions (AYC) comprising cell residue obtained by further treating the cell residue with acid solution, and removing acid solution-soluble components (hereinafter, yeast cell wall fractions (YCW) and acid-treated yeast cell wall fractions (ACW) are described collectively as yeast cell wall, not otherwise specified), have excellent physical properties as they have an excellent film property, and the film formed with these fractions have gas-barrier property. However, due to the coloring of yellow-brown to brown and to the typical odor and the like derived from yeast, the color, odor and the like could be an obstacle for the use as pharmaceuticals, foods and the like.
The present inventors have made a keen study to resolve the above-mentioned objects, and decolorized yeast cell wall fractions such as cell residue obtained by removing internal soluble cell components from enzyme-treated yeast, or cell residue obtained by further treating the cell residue with acid solution, and removing the acid solution-soluble components, removed the color and odor derived from yeast cell wall fraction without impairing excellent properties of the yeast cell wall fraction, such as film property and gas-barrier property of the formed film, and obtained a decolorized yeast cell wall fraction whose liquid YI (Yellow Index) is low (13 or under), and which has film property, and more preferably film disintegration property and they have found that a decolorized yeast cell wall fraction capable of preventing deterioration and the like of the coated material can be obtained by that treatment when the decolorized yeast cell wall fraction is used as a coating agent. Thus, the present invention has been completed.
The decolorized yeast cell wall fraction of the present invention can be used as an excellent coating agent, for example by exerting effectiveness also as inhibitor of volatilization and sublimation of agents containing volatilizing or sublimating substances, being a problem of “generation of whisker” in the field of medicinal preparation. “Whisker” herein mentioned relates to a phenomenon wherein volatilizing/sublimating substances in the solid preparation volatilize, and deposit spicular crystals on the surface of the solid preparation. When this phenomenon occurs, problems such as degradation of fluidity of the solid preparation or misconception with mold are pointed out.